This invention relates generally to tanks, and accessories therefor, and more specifically to insulated water tanks and associated plumbing for use in solar heating systems and a method and apparatus for insulating the tanks.
There has been a significant emphasis during the past several years on the development of solar heating systems. Typical solar heating systems which utilize water or other liquid as the heat transfer medium from the solar collectors to the point where heat is utilized incorporate a large volume liquid reservoir in which a large quantity of heated by the sun liquid can be stored. The storage tank or reservoir can be used in a number of ways: For example, it can contain the working fluid for the solar collector panels wherein the fluid is stored in the tank, pumped from the tank to the solar collector panels, circulated through the solar collector panels where it is heated and then returned to the storage tank, thereby maintaining the tank full of hot water as long as sufficient heat energy can be collected from the sun to keep the water hot. If the tank is of sufficiently large capacity, the hot water stored therein can serve as a supply source of heat for use in space heating a building, heating potable water, and the like for some period after the heat from the sun is no longer available. In this type of installation, heat from the water in the storage tank can be used for example to heat potable water for domestic use by positioning a heat exchanger in the storage tank and circulating potable water through the heat exchanger where heat is transferred from the fluid in the tank to the potable water. The potable water can then be piped to either a storage tank for heated potable water or to a point of use.
In systems wherein the working fluid must be an antifreeze solution to prevent freezing in cold weather or where it is desired to use other fluids more expensive than water, it is common to place the storage tank inside a building and maintain it full of water. The water in the tank is heated by circulating solar heated working fluid from the solar collector panels through a heat exchanger where heat is transferred from the working fluid into the water in the tank. Then, the heated water in the tank can be utilized as a supply of heat. For example, the hot water in the tank can be pumped to a point of use, such as a space heater, where the heat from the water is transferred to the air, and the water is then returned to the reservoir where it is reheated by the working fluid from the solar collector panels. Also, in this type of installation, a second heat exchanger for heating potable water can be positioned in the tank whereby heat can be transferred from the heated water in the tank to the potable water supply.
It is also conventional to provide a water supply inlet pipe to supply makeup water to keep the tank storage substantially full, a level switch in the tank for sensing a drop in water level and to activate a solenoid switch in the water makeup supply pipe to allow makeup water to flow into the tank. Also, it has been found useful to provide an electrically powered supplemental heating element in the storage tank for heating the water during periods when sufficient solar energy is not available to maintain the water at desired operating temperatures for the heating systems.
In the past, the various heat exchangers, supply tubes, switches, valves, supplementary heater elements and other components have been either positioned in the tank during manufacture or positioned therein through a number of individual openings in various locations in the tank. Such tank structures are not only expensive to manufacture, but they result in significant problems and expense, particularly when the components fail since it is sometimes impossible to remove the components for inspection or repair without diassembling or partially destroying the tank to do so. It also presents problems to manufacturers of tanks for use as storage tanks in solar heating systems, because they find it necessary to either fabricate tanks on an individual custom basis or to manufacture and maintain an inventory of a variety of tanks with different components fabricated therein to meet the varying needs and requirements of different solar heating systems designs.
Further, since the primary purpose of the storage tank in typical solar heating systems is to store and retain heated water for use in the heating systems, it is desirable to minimize heat loss from the tank to the environment by insulating the tank. Insulating large tanks in a manner which is durable, neat in appearance and effective has been a problem.